Its currently possible to drop the last refcount to the aux buffer
from NMI context, which results in the expected fireworks.
The refcounting needs a bigger overhaul, but to cure the immediate
problem, delay the freeing by using an irq_work.
Reviewed-and-tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150618103249.GK19282@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-static void rb_free_rcu(struct rcu_head *rcu_head)
-{
- struct ring_buffer *rb;
-
- rb = container_of(rcu_head, struct ring_buffer, rcu_head);
- rb_free(rb);
-}
-
struct ring_buffer *ring_buffer_get(struct perf_event *event)
{
struct ring_buffer *rb;
struct ring_buffer *ring_buffer_get(struct perf_event *event)
{
struct ring_buffer *rb;
struct ring_buffer {
atomic_t refcount;
struct rcu_head rcu_head;
struct ring_buffer {
atomic_t refcount;
struct rcu_head rcu_head;
+ struct irq_work irq_work;
#ifdef CONFIG_PERF_USE_VMALLOC
struct work_struct work;
int page_order; /* allocation order */
#ifdef CONFIG_PERF_USE_VMALLOC
struct work_struct work;
int page_order; /* allocation order */
};
extern void rb_free(struct ring_buffer *rb);
};
extern void rb_free(struct ring_buffer *rb);
+
+static inline void rb_free_rcu(struct rcu_head *rcu_head)
+{
+ struct ring_buffer *rb;
+
+ rb = container_of(rcu_head, struct ring_buffer, rcu_head);
+ rb_free(rb);
+}
+
extern struct ring_buffer *
rb_alloc(int nr_pages, long watermark, int cpu, int flags);
extern void perf_event_wakeup(struct perf_event *event);
extern struct ring_buffer *
rb_alloc(int nr_pages, long watermark, int cpu, int flags);
extern void perf_event_wakeup(struct perf_event *event);
+static void rb_irq_work(struct irq_work *work);
+
static void
ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
{
static void
ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
{
INIT_LIST_HEAD(&rb->event_list);
spin_lock_init(&rb->event_lock);
INIT_LIST_HEAD(&rb->event_list);
spin_lock_init(&rb->event_lock);
+ init_irq_work(&rb->irq_work, rb_irq_work);
+}
+
+static void ring_buffer_put_async(struct ring_buffer *rb)
+{
+ if (!atomic_dec_and_test(&rb->refcount))
+ return;
+
+ rb->rcu_head.next = (void *)rb;
+ irq_work_queue(&rb->irq_work);
+ ring_buffer_put_async(rb);
handle->event = NULL;
return NULL;
handle->event = NULL;
return NULL;
local_set(&rb->aux_nest, 0);
rb_free_aux(rb);
local_set(&rb->aux_nest, 0);
rb_free_aux(rb);
+ ring_buffer_put_async(rb);
void rb_free_aux(struct ring_buffer *rb)
{
if (atomic_dec_and_test(&rb->aux_refcount))
void rb_free_aux(struct ring_buffer *rb)
{
if (atomic_dec_and_test(&rb->aux_refcount))
+ irq_work_queue(&rb->irq_work);
+}
+
+static void rb_irq_work(struct irq_work *work)
+{
+ struct ring_buffer *rb = container_of(work, struct ring_buffer, irq_work);
+
+ if (!atomic_read(&rb->aux_refcount))
+
+ if (rb->rcu_head.next == (void *)rb)
+ call_rcu(&rb->rcu_head, rb_free_rcu);
}
#ifndef CONFIG_PERF_USE_VMALLOC
}
#ifndef CONFIG_PERF_USE_VMALLOC